Telecommunications networks have evolved from the earliest networks having few users with plain old telephone service (POTS) to networks in operation today interconnecting hundreds of millions of users with a wide variety of services including for example telephony, Internet, streaming video, and MPEG music. Central to these networks is the requirement for a switching fabric allowing different users to be connected either together or to a service provider. Supporting an increase in a number of users, connections and bandwidth are networks based upon segmentation, transmission, routing, detection and reconstruction of a signal. The segmentation results in a message being divided into segments—referred to as packets, and such networks being packet switched networks.
From a viewpoint of users, this process is transparent provided that the telecommunications network acts in a manner such that the packetization, and all other processes occur in a manner such that the user has available the services and information as required and “on demand.” The users perception of this “on demand” service varies substantially depending upon the service used. For example, when downloading most information via the Internet, a small delay is acceptable for text and photographs but not for streamed video unless sufficient memory buffer exists. Amongst the most sensitive services is telephony as the human perception of delay in voice is extremely acute. The result is that network providers prioritize packets according to information content, priority information included as part of the header of a packet.
The switching fabric of current telecommunications packet networks is a massive mesh of large electronic cross-connect switches interconnected generally by very high speed optical networks exploiting dense wavelength division multiplexing to provide interconnection paths offering tens of gigabit per second transmission. Within this mesh are a limited number of optical switches which generally provide protection switching and relatively slow allocation of bandwidth to accommodate demand.
But the demands from users for increased services, increased bandwidth and flexible services are causing the network operators to seek an alternative architecture. The alternative is “agile” networks which are widely distributed implementations of packet switching, as necessary to provide dynamic routing/bandwidth very close to users and with rapidly shifting patterns as they access different services. Agility to the network operators implies the ability to rapidly deploy bandwidth on demand at fine granularity. Helping them in this is the evolution of access networks which have to date been electrical at rates up to a few megabits per second but are now being replaced with optical approaches (often referred to as fiber-to-the-home or FTTH) with data rates of tens to hundreds of megabits per second to customers, and roadmaps to even gigabit rates per subscriber.
As the network evolves, and services become more flexible and expansive, speeds increase such that the network provider is increasingly focused to three problems:
Delay—the time taken to route packets across the network, where excessive delay in any single packet of a message prevents the message being completed
Mis-Sequencing—the mis-sequencing of packets through the network causes delays at the user as until the mis-sequenced packet arrives the message cannot be completed
Losses—the loss of packets due to blocked connections within the network causes delays as the lost packets must be retransmitted across the network.
It is therefore desirable within the network to address these issues with a physical switching fabric. The invention disclosed provides such an architecture for the distributed packet switching wherein the fabric acts to balance the traffic load on different paths and network elements within the distributed packet switch. In doing so the disclosed invention removes additionally the requirement for rapid reconfiguration of the packet switches, which has the added benefit of allowing the deployment of optical switches within the network which are slower and smaller than their electrical counterparts.